Rolling Stone journalist Michael Hastings had amphetamines and marijuana in his system when he crashed head-on into a tree in June and died on impact, the Los Angeles Coroner's office said in its autopsy report.

The report stated that Hastings' brothers told police upon finding out about his death that they had come to Los Angeles that very day to try and convince him to "go to detox."

Hastings, 33, had been sober for 14 years after earlier problems with drugs, one unnamed brother told Los Angeles police after being notified of the crash. He had been prescribed medical marijuana sometime before his crash and had been smoking it to deal with post-traumatic stress disorder from his war reporting in Afghanistan and Iraq, Hastings' brother told cops.

The brother told officers that Hastings had been smoking marijuana the night before the crash, and had been seen "passed out" at his house around midnight or 1 a.m., just hours before the 5 a.m. crash.

The coroner found traces of amphetamine in his system, and said the finding was consistent with intake of methamphetamine "many hours before death."

The report fiound that Hastings may have consumed marijuana hours before the crash, but that neither drug were responsible for Hastings careening off the side of a residential LA road and crashing into a tree. His official cause of death was listed as blunt force trauma consistent with a high-speed crash.

Hastings likely lost consciously immediately on impact and was likely killed within seconds, the report said. The car erupted into flames as it crashed, and charred much of Hastings' body after he was already dead, according to the coroner.

"(The brother) had just arrived from New York the day prior with another brother scheduled to arrive later this same morning, 6/18/13, as the family was attempting ot get (Hastings) to go to detox," the report read.

Hastings' brother informed cops that the young journalist had once had a problem with Ritalin, and had crashed his car into a pole several years earlier. He went to an in-patient rehab program around 1999, the report said.

Hastings was best known for his 2010 Rolling Stone profile of U.S. Army Gen. Stanley McChrystal, commander of U.S. forces in Afghanistan, which led to McChrystal's resignation. He also wrote for the website Buzzfeed.

After Hastings died in June, a close friend, Staff Sgt. Joseph Biggs, told KTLA he had received an email from Hastings just hours before his death saying that the FBI was investigating him, fueling conspiracy theories about Hastings' death on the Internet.

The FBI then put out a statement saying that they were not, in fact, investigating Hastings.